Bluefin Tuna Sampling

Work has kept us pretty busy lately, so in the spirit of adding new content as often as possible, I wanted to share some pictures from a few years ago. The Atlantic Bluefin Tuna, Thunnus thynnus is an incredibly large, fast growing, and pelagic fish native to just about the entire Atlantic basin. Our job was to take biological samples, including otoliths and fin clips, from recreationally landed fish for ageing and DNA samples. Unfortunately this is an incredibly dirty process, and I was unable and unwilling to subject my camera to the onslaught of oil and blood. Words cannot express how greasy these fish are! I did manage to take a few cell phone photographs of some of the age structures, but a majority of the photos were of the unloading process, and not of the sampling.

Initially, the fish are tagged, and hoisted off the boat. During the hoist, the fish are weighed for an initial weight.

Bluefin Tuna Processing

Bluefin Tuna Processing

Bluefin Tuna Processing

You will notice in the second picture, that the operculum and gills have been removed. This is done by the angler’s at sea, in order to cool the fish down as quickly as possible after the long fight. The gill cavity is then filled with ice for the ride back in.

Bluefin Tuna Processing

Once the fish are off the boat and weighed, they are measured using the curved fork length. This information will be submitted along with the tag numbers to federal and state fisheries. The fish are then picked back up, and lowered onto a cleaning table, this is where the job gets messy!

Bluefin Tuna Processing

The dorsal, anal, and pectoral fins are cut off first:

Bluefin Tuna Processing

Then the head is removed:

Bluefin Tuna Processing

Bluefin Tuna Processing

Next up, the caudal fin:

Bluefin Tuna Processing

Now the remaining gills, and all of the guts!

Bluefin Tuna Processing

Bluefin Tuna Processing

Bluefin Tuna Processing

Bluefin Tuna Processing

What is left is then loaded into a harness and craned into a deep freezer for the ride to the market. (Most likely in Japan, although some NY and LA restaurants will buy them)

Bluefin Tuna Processing

Until sometime in the 1970’s, bluefin tuna wasn’t really marketed for human consumption, as it is an in incredibly bloody fish. Old timers talk about selling them to dog food manufacturers, or to burying parts of them in their gardens for fertilizer. How much of this talk is just hyperbole, I don’t know, however in today’s market, these fish command very high prices, and I can’t imagine any dogs getting to enjoy it.